10.4.6 Towards what Objective Should the Response Be Targetted? High versus
Low Stabilization Levels Insights on Mitigation

In a rational world, the ultimate level of climate and thus GHG concentration
stabilization would emerge from a political process in which the global community
would weigh mitigation costs and the averted damages associated with different
levels of stabilization. Also weighed would be the risks of triggering systemic
changes in large geophysical systems, like ocean circulation, or other irreversible
impacts. In reality, the political process will inevitably be influenced by
the distribution of positive and negative effects of climate change, as well
as by the costs of mitigation among countries, largely determined by how risks,
costs, environmental values, and development aspirations are weighed in different
regions and cultures. This process will be strongly influenced by new scientific
and technical knowledge and by experience gained in making and implementing
policy. The climate change literature contains a diversity of arguments as to
why either a low level or a relatively high level of stabilization is desirable
(IPCC, 2001b).

Given the large uncertainties that characterize each component of the climate
change problem, it is impossible to establish a globally acceptable level of
stabilized GHG concentrations today. Studies discussed in this section and summarized
in Table 10.11 support the obvious expectations that
lower stabilization targets involve exponentially higher mitigation costs and
relatively more ambitious near-term emissions reductions, but, as reported by
WGII (IPCC, 2001b), lower targets induce significantly smaller biological and
geophysical impacts and thus induce smaller damages and adaptation costs.